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Sometimes it is important to be able to wait a short period of time in an ASP or VB
application before continuing on. Most recently, I had to write an application that
used Site Server content replication to migrate files from one folder to another. In
order to ensure that the process completed successfully, I had to check the process's
status periodically and wait for it to either fail or succeed. Obviously, I could have
done a WHILE ERR<>0...WEND loop, but that would have been unnecessarily harsh on the
cpu -- I really don't need to check the status of the process a thousand times per
second.
So, this component, Timer.Sleep, uses the windows kernel Sleep command, and is only
a few lines of code. It has one method, DoSleep, which takes one parameter, the number
of milliseconds to sleep. You can download the component DLL here:
Timer.dll (20k)
The source code for the example is:
1 <% OPTION EXPLICIT %>
2 <%
3 'Try to avoid buffering and caching...
4 Response.Buffer = False
5 Response.Expires = 0
6 Response.ExpiresAbsolute = Now() - 1
7 Response.AddHeader "cache-control", "private"
8 Response.AddHeader "pragma", "no-cache"
9 Server.ScriptTimeout = 0
10 %>
11 <!-- #INCLUDE VIRTUAL="/stevesmith/include/articleformat.asp" -->
12 <!-- #INCLUDE VIRTUAL="/stevesmith/include/DisplayStatusMessage.asp" -->
13 <%
14 Response.Write("This example is no longer supported - the COM object is no longer installed on this server.")
15 Response.End
16 'Declare Variables
17 Dim objTimer
18 Dim I
19 Dim strCountdown
20
21 'Instantiate components
22 Set objTimer = Server.CreateObject("Timer.Sleep")
23
24 'Display top of page template
25 Call ArticleHeader("Sleep/Timer Example","","")
26 %>
27 <p>
28 <b>Look at your status bar at the bottom of your browser.</b>
29 </p>
30 <p>This is a very simple example that demonstrates the use of the timer
31 dll. We're going to be writing to the status bar of your browser, once per second,
32 with a countdown.
33 </p>
34 <p>
35 <b>Note:</b>
36 If your browser is set up to cache web pages, you may not see the countdown take place
37 after your first visit to this page.
38 </p>
39 <%
40
41 'Display bottom of page template
42 Call ArticleFooter()
43
44 'Count down from 10 to 0, then display LIFTOFF in the status window
45 For I = 10 To 0 Step -1
46 Call objTimer.DoSleep(1000)
47 strCountdown = strCountdown & I & "... "
48 If I = 0 Then
49 strCountdown = strCountdown & " LIFTOFF!!!"
50 End If
51 DisplayStatusMessage(strCountdown)
52 Next
53 %>
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The included file that writes to the status window is documented here:
1 <%
2 Public Sub DisplayStatusMessage(strMessage)
3 Dim NL
4 NL = chr(10) & chr(13)
5 Response.Write "<script type=" & Chr(34) & "text/javascript" & Chr(34) & ">" & NL
6 Response.Write "<!--" & NL
7 Response.Write "parent.window.status = '" & strMessage & "';" & NL
8 Response.Write "//--></script>"
9 End Sub
10 %>
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